Advanced analysis systems have a number of important desired performance characteristics, namely accuracy, reliability, selectivity for target analytes, quantitation, low detection limits, simplicity, speed, cost, multiplexing, and so on. Frequently, there is a tradeoff between these objectives (e.g., low cost vs. high accuracy), requiring a compromise that best meets the analysis requirements. For example, the performance of benchtop analyzers takes precedence over portability, while for point-of-care (POC) systems, versatility and performance are often sacrificed in favor of convenience.
A number of automated and robust laboratory-based systems are available for analyses. Liquid chromatography1 is widely used and has seen recent progress in stationary phases2, 3 and with increased pressures.4 Mass spectrometry methods5, 6 have advanced through improved mass analyzers7 and sample introduction techniques.8 Spectroscopy can provide analyte-specific information from absorbance9 or Raman10 techniques. In addition, clinical diagnostic tools11 such as enzyme-linked immunosorbent assay (ELISA)12 are broadly used for targeted detection of biomolecules of interest. The above examples nicely illustrate systems with excellent performance, but that capability generally comes at the expense of portability.
On the other hand, portable instruments offer significantly increased analysis convenience. For example, POC diagnostic devices have been implemented in monitoring blood glucose for diabetes13 and in home pregnancy testing.14 Paper-based microfluidic systems15-17 offer simplified analysis coupled with low cost. These portable systems are advantageous in terms of simplicity and speed, but this generally comes at the cost of some performance characteristics such as low detection limits, quantitation capabilities, or multiplexing.